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 * Copyright (c) 2007, 2009, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.nio.file.attribute;

import java.io.IOException;

/**

 * An object to lookup user and group principals by name. A {@link UserPrincipal}

 * represents an identity that may be used to determine access rights to objects

 * in a file system. A {@link GroupPrincipal} represents a <em>group identity</em>.

 * A {@code UserPrincipalLookupService} defines methods to lookup identities by

 * name or group name (which are typically user or account names). Whether names

 * and group names are case sensitive or not depends on the implementation.

 * The exact definition of a group is implementation specific but typically a

 * group represents an identity created for administrative purposes so as to

 * determine the access rights for the members of the group. In particular it is

 * implementation specific if the <em>namespace</em> for names and groups is the

 * same or is distinct. To ensure consistent and correct behavior across

 * platforms it is recommended that this API be used as if the namespaces are

 * distinct. In other words, the {@link #lookupPrincipalByName

 * lookupPrincipalByName} should be used to lookup users, and {@link

 * #lookupPrincipalByGroupName lookupPrincipalByGroupName} should be used to

 * lookup groups.

 *

 * @since 1.7

 *

 * @see java.nio.file.FileSystem#getUserPrincipalLookupService

 */

public abstract class UserPrincipalLookupService {

    /**

     * Initializes a new instance of this class.

     */

    protected UserPrincipalLookupService() {

    }

    /**

     * Lookup a user principal by name.

     *

     * @param   name

     *          the string representation of the user principal to lookup

     *

     * @return  a user principal

     *

     * @throws  UserPrincipalNotFoundException

     *          the principal does not exist

     * @throws  IOException

     *          if an I/O error occurs

     * @throws  SecurityException

     *          In the case of the default provider, and a security manager is

     *          installed, it checks

     *          {@link RuntimePermission}{@code ("lookupUserInformation")}

     */

    public abstract UserPrincipal lookupPrincipalByName(String name)

        throws IOException;

    /**

     * Lookup a group principal by group name.

     *

     * <p> Where an implementation does not support any notion of group then

     * this method always throws {@link UserPrincipalNotFoundException}. Where

     * the namespace for user accounts and groups is the same, then this method

     * is identical to invoking {@link #lookupPrincipalByName

     * lookupPrincipalByName}.

     *

     * @param   group

     *          the string representation of the group to lookup

     *

     * @return  a group principal

     *

     * @throws  UserPrincipalNotFoundException

     *          the principal does not exist or is not a group

     * @throws  IOException

     *          if an I/O error occurs

     * @throws  SecurityException

     *          In the case of the default provider, and a security manager is

     *          installed, it checks

     *          {@link RuntimePermission}{@code ("lookupUserInformation")}

     */

    public abstract GroupPrincipal lookupPrincipalByGroupName(String group)

        throws IOException;

}